Файл: The PIC Microcontroller Book for beginning (Nebojsa Matic).pdf

PIC book

PIC microcontrollers for beginners,too!

Author: Nebojsa Matic

Paperback - 252 pages (May 15, 2000)

Dimensions (in inches): 0.62 x 9.13 x 7.28

PIC microcontrollers; low-cost computers-in-a-chip; allows electronics designers and hobbyists add intelligence and functions that mimic big computers for almost any electronic product or project.

The purpose of this book is not to make a microcontroller expert out of you, but to make you equal to those who had someone to go to for their answers.

In this book you can find:

Practical connection samples for

Relays, Optocouplers, LCD's, Keys, Digits, A to D Converters, Serial communication etc.

Introduction to microcontrollers

Learn what they are, how they work, and how they can be helpful in your work.

Assembler language programming

How to write your first program, use of macros, addressing modes....

Instruction Set

Description, sample and purpose for using each instruction........

MPLAB program package

How to install it, how to start the first program, following the program step by step in the simulator....

C o n t e n t s

CHAPTER I INTRODUCTION TO MICROCONTROLLERS

Introduction

History

Microcontrollers versus microprocessors

1.1 Memory unit

1.2 Central processing unit

1.3 Buses

1.4 Input-output unit

1.5 Serial communication

1.6 Timer unit

1.7 Watchdog

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1.8 Analog to digital converter

1.9 Program

CHAPTER II MICROCONTROLLER PIC16F84

Introduction

CISC, RISC

Applications

Clock/instruction cycle

Pipelining

Pin description

2.1 Clock generator - oscillator

2.2 Reset

2.3 Central processing unit

2.4 Ports

2.5 Memory organization

2.6 Interrupts

2.7 Free timer TMR0

2.8 EEPROM Data memory

CHAPTER III INSTRUCTION SET

Introduction

Instruction set in PIC16Cxx microcontroller family Data Transfer

Arithmetic and logic Bit operations

Directing the program flow Instruction execution period Word list

CHAPTER IV ASSEMBLY LANGUAGE PROGRAMMING

Introduction

Sample of a written program

Control directives

●4.1 define

●4.2 include

●4.3 constant

●4.4 variable

●4.5 set

●4.6 equ

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●4.7 org

●4.8 end

Conditional instructions

●4.9 if

●4.10 else

●4.11 endif

●4.12 while

●4.13 endw

●4.14 ifdef

●4.15 ifndef

Data directives

●4.16 cblock

●4.17 endc

●4.18 db

●4.19 de

●4.20 dt

Configurating a directive

●4.21 _CONFIG

●4.22 Processor

Assembler arithmetic operators

Files created as a result of program translation Macros

CHAPTER V MPLAB

Introduction

5.1 Installing the MPLAB program package

5.2 Introduction to MPLAB

5.3 Choosing the development mode

5.4 Designing a project

5.5 Designing new assembler file

5.6 Writing a program

5.7 MPSIM simulator

5.8 Toolbar

CHAPTER VI THE SAMPLES

Introduction

6.1 The microcontroller power supply

6.2 Macros used in programs

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●Macros WAIT, WAITX

●Macro PRINT

6.3 Samples

●Light Emitting Diodes

●Keyboard

●Optocoupler

Optocouplering the input lines

Optocouplering the output lines

●Relays

●Generating a sound

●Shift registers

Input shift register

Output shift register

●7-segment Displays (multiplexing)

●LCD display

●12-bit AD converter

●Serial communication

APPENDIX A INSTRUCTION SET

APPENDIX B NUMERIC SYSTEMS

Introduction

B.1 Decimal numeric system

B.2 Binary numeric system

B.3 Hexadecimal numeric system

APPENDIX C GLOSSARY

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CHAPTER 1

Introduction to Microcontrollers

Introduction

History

Microcontrollers versus microprocessors

1.1 Memory unit

1.2 Central processing unit

1.3 Buses

1.4 Input-output unit

1.5 Serial communication

1.6 Timer unit

1.7 Watchdog

1.8 Analog to digital converter

1.9 Program

Introduction

Circumstances that we find ourselves in today in the field of microcontrollers had their beginnings in the development of technology of integrated circuits. This development has made it possible to store hundreds of thousands of transistors into one chip. That was a prerequisite for production of microprocessors , and the first computers were made by adding external peripherals such as memory, input-output lines, timers and other. Further increasing of the volume of the package resulted in creation of integrated circuits. These integrated circuits contained both processor and peripherals. That is how the first chip containing a microcomputer , or what would later be known as a microcontroller came about.

History

It was year 1969, and a team of Japanese engineers from the BUSICOM company arrived to United States with a request that a few integrated circuits for calculators be made using their projects. The proposition was set to INTEL, and Marcian Hoff was responsible for the project.

Since he was the one who has had experience in working with a computer (PC) PDP8, it occured to him to suggest a fundamentally different solution instead of the suggested construction. This solution presumed that the function of the integrated circuit is determined by a program stored in it. That meant that configuration would be more simple, but that it would require far more memory than the project that was proposed by Japanese engineers would require. After a while, though Japanese engineers tried finding an easier solution, Marcian's idea won, and the first microprocessor was born. In transforming an idea into a ready made product , Frederico Faggin was a major help to INTEL. He transferred to INTEL, and in only 9 months had succeeded in making a product from its first conception. INTEL obtained the rights to sell this integral block in 1971. First, they bought the license from the BUSICOM company who had no

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Chapter 1 - Introduction to Microprocessors

idea what treasure they had. During that year, there appeared on the market a microprocessor called 4004. That was the first 4-bit microprocessor with the speed of 6 000 operations per second. Not long after that, American company CTC requested from INTEL and Texas Instruments to make an 8-bit microprocessor for use in terminals. Even though CTC gave up this idea in the end, Intel and Texas Instruments kept working on the microprocessor and in April of 1972, first 8-bit microprocessor appeard on the market under a name 8008. It was able to address 16Kb of memory, and it had 45 instructions and the speed of 300 000 operations per second. That microprocessor was the predecessor of all today's microprocessors. Intel kept their developments up in April of 1974, and they put on the market the 8-bit processor under a name 8080 which was able to address 64Kb of memory, and which had 75 instructions, and the price began at $360.

In another American company Motorola, they realized quickly what was happening, so they put out on the market an 8-bit microprocessor 6800. Chief constructor was Chuck Peddle, and along with the processor itself, Motorola was the first company to make other peripherals such as 6820 and 6850. At that time many companies recognized greater importance of microprocessors and began their own developments. Chuck Peddle leaved Motorola to join MOS Technology and kept working intensively on developing microprocessors.

At the WESCON exhibit in United States in 1975, a critical event took place in the history of microprocessors. The MOS Technology announced it was marketing microprocessors 6501 and 6502 at $25 each, which buyers could purchase immediately. This was so sensational that many thought it was some kind of a scam, considering that competitors were selling 8080 and 6800 at $179 each. As an answer to its competitor, both Intel and Motorola lowered their prices on the first day of the exhibit down to $69.95 per microprocessor. Motorola quickly brought suit against MOS Technology and Chuck Peddle for copying the protected 6800. MOS Technology stopped making 6501, but kept producing 6502. The 6502 was a 8-bit microprocessor with 56 instructions and a capability of directly addressing 64Kb of memory. Due to low cost , 6502 becomes very popular, so it was installed into computers such as: KIM-1, Apple I, Apple II, Atari, Comodore, Acorn, Oric, Galeb, Orao, Ultra, and many others. Soon appeared several makers of 6502 (Rockwell, Sznertek, GTE, NCR, Ricoh, and Comodore takes over MOS Technology) which was at the time of its prosperity sold at a rate of 15 million processors a year!

Others were not giving up though. Frederico Faggin leaves Intel, and starts his own Zilog Inc. In 1976 Zilog announced the Z80. During the making of this microprocessor, Faggin made a pivotal decision. Knowing that a great deal of programs have been already developed for 8080, Faggin realized that many would stay faithful to that microprocessor because of great expenditure which redoing of all of the programs would result in. Thus he decided that a new processor had to be compatible with 8080, or that it had to be capable of performing all of the programs which had already been written for 8080. Beside these characteristics, many new ones have been added, so that Z80 was a very powerful microprocessor in its time. It was able to address directly 64 Kb of memory, it had 176 instructions, a large number of registers, a built in option for refreshing the dynamic RAM memory, single-supply, greater speed of work etc. Z80 was a great success and everybody converted from 8080 to Z80. It could be said that Z80 was without a doubt commercially most successful 8-bit microprocessor of that time. Besides Zilog, other new manufacturers like Mostek, NEC, SHARP, and SGS also appeared. Z80 was the heart of many computers like Spectrum, Partner, TRS703, Z-3 .

In 1976, Intel came up with an improved version of 8-bit microprocessor named 8085. However, Z80 was so much better that Intel soon lost the battle. Altough a few more processors appeared on the market (6809, 2650, SC/MP etc.), everything was actually already decided. There weren't any more great improvements to make manufacturers convert to something new, so 6502 and Z80 along with 6800 remained as main representatives of the 8- bit microprocessors of that time.

Microcontrollers versus Microprocessors

Microcontroller differs from a microprocessor in many ways. First and the most important is its functionality. In order for a microprocessor to be used, other components such as memory, or

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components for receiving and sending data must be added to it. In short that means that microprocessor is the very heart of the computer. On the other hand, microcontroller is designed to be all of that in one. No other external components are needed for its application because all necessary peripherals are already built into it. Thus, we save the time and space needed to construct devices.

1.1 Memory unit

Memory is part of the microcontroller whose function is to store data.

The easiest way to explain it is to describe it as one big closet with lots of drawers. If we suppose that we marked the drawers in such a way that they can not be confused, any of their contents will then be easily accessible. It is enough to know the designation of the drawer and so its contents will be known to us for sure.

Memory components are exactly like that. For a certain input we get the contents of a certain addressed memory location and that's all. Two new concepts are brought to us: addressing and memory location. Memory consists of all memory locations, and addressing is nothing but selecting one of them. This means that we need to select the desired memory location on one hand, and on the other hand we need to wait for the contents of that location. Beside reading from a memory location, memory must also provide for writing onto it. This is done by supplying an additional line called control line. We will designate this line as R/W (read/write). Control line is used in the following way: if r/w=1, reading is done, and if opposite is true then writing is done on the memory location. Memory is the first element, and we need a few operation of our microcontroller .

1.2 Central Processing Unit

Let add 3 more memory locations to a specific block that will have a built in capability to multiply, divide, subtract, and move its contents from one memory location onto another. The part we just added in is called "central processing unit" (CPU). Its memory locations are called registers.

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Registers are therefore memory locations whose role is to help with performing various mathematical operations or any other operations with data wherever data can be found. Look at the current situation. We have two independent entities (memory and CPU) which are interconnected, and thus any exchange of data is hindered, as well as its functionality. If, for example, we wish to add the contents of two memory locations and return the result again back to memory, we would need a connection between memory and CPU. Simply stated, we must have some "way" through data goes from one block to another.

1.3 Bus

That "way" is called "bus". Physically, it represents a group of 8, 16, or more wires

There are two types of buses: address and data bus. The first one consists of as many lines as the amount of memory we wish to address, and the other one is as wide as data, in our case 8 bits or the connection line. First one serves to transmit address from CPU memory, and the second to connect all blocks inside the microcontroller.

As far as functionality, the situation has improved, but a new problem has also appeared: we have a unit that's capable of working by itself, but which does not have any contact with the outside world, or with us! In order to remove this deficiency, let's add a block which contains several memory locations whose one end is connected to the data bus, and the other has connection with the output lines on the microcontroller which can be seen as pins on the electronic component.

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1.4 Input-output unit

Those locations we've just added are called "ports". There are several types of ports : input, output or bidiectional ports. When working with ports, first of all it is necessary to choose which port we need to work with, and then to send data to, or take it from the port.

When working with it the port acts like a memory location. Something is simply being written into or read from it, and it could be noticed on the pins of the microcontroller.

1.5 Serial communication

Beside stated above we've added to the already existing unit the possibility of communication with an outside world. However, this way of communicating has its drawbacks. One of the basic drawbacks is the number of lines which need to be used in order to transfer data. What if it is being transferred to a distance of several kilometers? The number of lines times number of kilometers doesn't promise the economy of the project. It leaves us having to reduce the number of lines in such a way that we don't lessen its functionality. Suppose we are working with three lines only, and that one line is used for sending data, other for receiving, and the third one is used as a reference line for both the input and the output side. In order for this to work, we need to set the rules of exchange of data. These rules are called protocol. Protocol is therefore defined in advance so there wouldn't be any misunderstanding between the sides that are communicating with each other. For example, if one man is speaking in French, and the other in English, it is highly unlikely that they will quickly and effectively understand each other. Let's suppose we have the following protocol. The logical unit "1" is set up on the transmitting line until transfer begins. Once the transfer starts, we lower the transmission line to logical "0" for a period of time (which we will designate as T), so the receiving side will know that it is receiving data, and so it will activate its mechanism for reception. Let's go back now to the transmission side and start putting logic zeros and ones onto the transmitter line in the order from a bit of the lowest value to a bit of the highest value. Let each bit stay on line for a time period which is equal to T, and in the end, or after the 8th bit, let us bring the logical unit "1" back on the line which will mark the end of the transmission of one data. The protocol we've just described is called in professional literature NRZ (Non-Return to Zero).

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